1. Field of the Invention
The present invention relates to a technique for supporting in a vibration proof manner the mechanical chassis of a reproduction device equipped with a reading mechanism for reading data in a non-contact manner from a disc-like recording medium, such as a CD, CD-ROM, CD-RW, DVD, DVD-ROM/RAM, or a magneto-optical disc device, for use in audio apparatus, video apparatus, information apparatus, various types of precision apparatus, and so forth, including automotive and commercial uses.
2. Description of the Related Art
In reproduction devices for disc-like recording media as mentioned above (hereinafter referred to as disc), there is a trend toward increasing the rotation speed when performing data reading. This also applies to reproduction devices of the type capable of data writing. Thus, it is a constant challenge to damp vibration of the reproduction device transmitted from outside (hereinafter referred to as external vibration), rotation vibration of the eccentric disc, and vibration generated by the driving mechanisms, such as the disc rotating motor and pickup (hereinafter referred to as internal vibration). Due to the non-contact type reading/writing system, such external vibration and internal vibration have a significantly bad effect on the reading accuracy and writing accuracy.
As indispensable vibration damping means for solving this problem, a vibration proof structure as shown in FIGS. 11A through 13B is known, in which dampers 5, 6 are provided between a casing 2 of a reproduction device 1 and a mechanical chassis 4 for driving a disc 3 for reproduction, the mechanical chassis 4 being elastically supported in a vibration proof manner.
One of the typical dampers used in such a vibration proof structure is an insulation-type damper, as shown in FIG. 11B. This damper 5 is formed of a rubber-like elastic material in a substantially cylindrical configuration. In its outer peripheral surface, there is formed a mounting groove 5a to be engaged with a mounting portion 4a of the mechanical chassis 4.
Another typical damper is one with viscous fluid sealed in, as shown in FIG. 12A. This damper 6 comprises a cylindrical peripheral wall portion 6a formed of a hard resin, such as polypropylene, a flexible portion 6b closing the opening at one end thereof and formed of a rubber-like elastic material such as thermoplastic elastomer, a lid portion 6c closing the opening at the other end and formed of a hard resin such as polypropylene, and a liquid viscous fluid 6d consisting of silicone oil or the like sealed in the internal space defined by the peripheral wall portion 6a, the flexible portion 6b, and the lid portion 6c. The damper 6 can be used in conjunction with coil springs S, as shown in FIGS. 13A and 13B.
In the former insulator type damper 5, it is difficult to set the spring constant so as to satisfy the requisite vibration control performance for the reproduction device 1, in which there is a marked increase in the rotation speed of the disc, so that a sufficient vibration damping effect is not to be expected. In view of this, the latter type of damper 6 with sealed-in viscous fluid, which is superior in damping effect, is frequently used. This, however, has the following problems.
As shown, for example, in FIG. 13A, in the condition in which the reproduction device 1 is placed in the horizontal position, the damper 6 is mounted so as to face a side plate 2a extending in the transverse direction (thickness direction) y of the structure member of the reproduction device 1, i.e., the casing 2. The damper 6 has in the lid portion 6c a mounting portion including a hole 6e for passing a screw N for fixing the damper to the side plate 2a. Thus, the thickness t2 of the entire reproduction device including the height t1 of the side plate 2a is considerably large. If the reproduction device is further reduced in thickness, the mounting of the damper 6 becomes impossible. Thus, with the prevention of vibration for the mechanical chassis 4 by using this damper 6, there is a limitation to a further reduction in the thickness of the reproduction device 1, with the distance L necessary in terms of the mechanism of the reproduction device 1 being secured between the disc 3 and the top plate of the casing 2.
In the case in which, as shown in FIG. 13B, the lid portion 6c is mounted to the structure member of the reproduction device 1 placed horizontally, i.e., in the case in which the damper 6 is mounted so as to face the bottom plate 2b extending along the longitudinal direction x of the casing 2, even when the same distance L is secured between the disc 3 and the top plate of the casing 2, the total thickness t3 of the reproduction device 1 can be made somewhat smaller than the total thickness t2 in FIG. 13A. However, this is still insufficient to meet the requirement for a further reduction in size, and there is a demand for a damper different from the damper 6, and a vibration proof structure for the mechanical chassis 4, which can meet the requirement for a further reduction in the thickness of the reproduction device 1.
Further, in both the mounting structures for the damper 6 shown in FIGS. 13A and 13B, the lid portion 6c is mounted so as to face the side plate 2a or the bottom plate 2b of the casing 2, so that it is necessary to secure the requisite mounting area for the flat lid portion 6c in the side plate 2a and the bottom plate 2b. Thus, there can be a limitation to the configuration of the side plate 2a and the bottom plate 2b. For example, the bead for the reinforcement of the casing 2 cannot be formed, or there is a limitation to the mounting positions for other parts to be mounted to the side plate 2a and the bottom plate 2b. 
These problems also apply to a so-called air damper in which, instead of using the liquid viscous fluid 6d as the damping medium, air holes are formed in the peripheral wall portion 6a and the lid portion 6c, and a damping effect is obtained from the air flowing through the air holes.